The present invention relates to a liquid crystal display (LCD) device. More particularly, the present invention relates to the LCD device including a tiling panel in which a plurality of discrete LCD panels are bonded together to form a large size display screen.
The LCD device using as the tiling panel has been developed, in which a plurality of discrete LCD panels are bonded together. FIG. 1 shows the LCD device using the tiling panel to which the technology of the present invention is applicable. In the FIG. 1, the tiling panel includes four discrete LCD panels A, B, C and D, for example, which are bonded together along a bonding region 19. A cross point of the vertical bonding region 19 and the horizontal bonding region 19 is a center point (CT) of the tiling panel. Each of the LCD panels A, B, C and D includes a lower glass substrate 1 and an upper glass substrate 2. Next, the positional relationship of the pixels of the LCD panels A, B, C and D, which are located adjacent to the bonding region 19, is described. FIG. 2 shows an arrangement of pixel regions of the LCD panels A, B, C and D. It is assumed that a width of a black matrix disposed between the adjacent two pixel region in the horizontal direction is LH, and a width of the black matrix disposed between the adjacent two pixel regions in the vertical direction is LV. To display the natural and continuous image across the bonding regions 19, the distance between the pixel region PMN at the most lower right position of the panel A and the pixel region PM1 at the most lower left position of the panel B, and the distance between the pixel region P1N at the most upper, right position of the panel D and the pixel region P11 at the most upper left position of the panel C should be the distance represented by 2L1+LB, wherein the L1 less than LH/2, and LB is the width of the bonding region 19. Further, the distance between the pixel region PMN of the panel A and the pixel region P1N of the panel D, and the distance between the pixel region PM1 of the panel B and the pixel region P11 of the panel C should be the distance represented by 2L2+LB, wherein the L2 less than LV/2. A sealing regions 8, later described, are shown by the dashed line in the FIG. 2.
Describing a structure of one LCD panel, such as the LCD panel A, used for the tiling panel, with reference to FIG. 3. The FIG. 3 shows the structure on the lower glass substrate 1 and the upper glass substrate 2 of the panel A. On the surface of the lower glass substrate 1, a plurality of data lines DL1 through DLN are formed along the vertical direction, a plurality of gate lines GL1 through GLM are formed along the horizontal direction, one pixel region including a thin film transistor (TFT) 3 and the pixel electrode 4 defining one pixel (P) is formed at each of the cross points of the data lines and the gate lines, an outer short ring 5 and an inner short ring 6 made of an electrically conductive material are formed, and an alignment layer made of polyimide, not shown in the FIGS. 1 and 2 are formed. The arrangement of the liquid crystal molecules is decided by a rubbing direction on the surface of the alignment layer, in the rubbing process. On the surface of the upper glass substrate 2, a common electrode and the alignment layer, not shown in the FIGS. 1 and 2, are formed. In the case of a color LCD device, color filters, i.e. Red color filters, Green color filters and Blue color filters, are formed on the upper glass substrate 2.
At the completion of the lower glass substrate 1, both the outer and inner short rings 5 and 6 are formed. The lower glass substrate 1 is cut along cutting lines 9A through 9D, so that the outer short ring 5 and the right side portion and the lower portion of the inner short ring 6 are removed. Before the cutting process, the outer short ring 5 is connected to a potential level corresponding to the potential level of the common electrode. The outer short ring 5 is connected to the inner short ring 6 through resistive element 7. Each of the data lines DL1 through DLN is connected to the outer short ring 5 and the inner short ring 6 through the resistive element 7, respectively, and each of the gate lines GL1 through GLM is connected to the outer short ring 5 and the inner short ring 6 through the resistive element 7, respectively. The purpose of the outer and inner short rings 5 and 6 is to prevent the TFT 3 of the pixel region from being damaged by electrostatic discharge (ESD) during the fabrication of the LCD panel, in the following manner. A resistive value of the resistive element 7, such as a TFT operating as a diode, is designed to be lower than a resistive value of the TFT 3 of the pixel region. When the electrostatic charges are applied to the gate lines, for example, during the handling of the lower glass substrate 1, the resistive element 7 connected between the gate lines and the short ring 6, and the resistive element 7 connected between the short ring 8 and the data lines conduct, whereby the electric potential level at the gate lines becomes equal to the electric potential at the data lines, and no voltage is applied between the drain and gate electrodes of the TFT 3 of the pixel region. After the cutting of the lower glass substrate 1 and the assemble of the upper glass substrate 2 on the lower glass substrate 1, the inner short ring 6 is connected to the common electrode on the upper glass substrate 2, so that when the electrostatic charges are applied to the gate line(s) or the data line(s), the resistive elements 7 conduct to pass the electrostatic charges to the common electrode through the inner ring 6, resulting that the electric potential level at the lower glass substrate 1 becomes equal to the electric potential of the common electrode on at the upper glass substrate 2, and no voltage is applied to the TFT 3 of the pixel region.
The lower glass substrate 1 and the upper glass substrate 2 are sealed along the sealing region 8 to complete the panel A, as well known in the art. Describing the formation of the sealing region 8 of the panel A with reference to the FIG. 2, the right side portion of the sealing region 8 is formed adjacent to the pixel regions of the right most data line DLN, and the lower side portion of the sealing region 8 is formed adjacent to the pixel regions of the lower most gate line GLM, to provide the distance L1 and the distance L2 (FIG. 2), respectively after the cutting process. It is required to provide the positional relationship of the pixel regions on the LCD panels A, B, C and D, as shown in the FIG. 2. For this reason, the right side and lower side portions of the sealing region 8 are formed inside of the inner short ring 6. A typical width W1 of the sealing region 8 is about 500 through 1000 xcexcm, and the width W2 of the sealing area 8 remaining along the cutting lines 9B and 9D is about 50 through 100 xcexcm. Therefore, the LCD panel A includes the short ring 6 along the upper side and the left side, and does not include the short ring 6 along the right side and the lower side. A flexible circuit board or TAB (Tape Automated Bonding) tape, on which circuit modules, such as data line drivers are mounted, is connected to the data lines, which are exposed in an upper side area 10 (FIG. 3), and a flexible circuit board or the TAB tape, on which circuit modules, such as gate line drivers are mounted, is connected to the gate lines, which are exposed on a left side area 11 (FIG. 3). In a similar manner as the LCD panel A, the LCD panels B, C and D are formed by changing the position of the cutting lines.
The four LCD panels A, B, C and D constitutes one LCD display screen, and the data line drivers of the four LCD panels and the gate line drivers of the four LCD panels are controlled to display the image on the four LCD panels.
To bond the LCD panels, a light shielding and insulating adhesive, as shown in Japanese Published Examined Patent Application 2-59999, has been used. A first problem is that, during the handling of the completed tiling panel using the light shielding and insulating adhesive, a large quantity of electrostatic charges are accumulated on the completed tiling panel, and the TFTs 3 of the pixel regions adjacent to the bonding region 19 are damaged, for the reason that after that a plurality of LCD panels have been assembled on a supporting glass substrate 26, as shown in FIG. 4, a total surface area of the completed tiling panel becomes large, and hence a large quantity of electrostatic charges accumulated due to a friction induced during the handling of the completed tiling panel, and the accumulated electrostatic charges tend to discharge to the data line(s) or the gate line(s) proximity to the bonding region 19.
It is required that all the four LCD panels A, B, C and D have the same display characteristic, i.e. as a wide viewing angle providing a good contrast ratio. The user usually sees the LCD device along a lower side direction L, which located at the lower side of a vertical line to the surface of the FIG. 1, and hence, the rubbing direction of the alignment layer of the four LCD panels A, B, C and D, as shown in the FIG. 1 have been used to realize the wide viewing angle providing the good contrast ratio in the lower side direction L. In the
FIG. 1, an arrow with double dotted line indicates the rubbing direction of the alignment layer on the lower glass substrate 1, and an arrow with a single solid line indicates the rubbing direction of the alignment layer of the upper glass substrate 2.
For the above reason, the same rubbing direction, i.e. the direction from the upper left region to the lower right region, is used in the alignment layers of the lower glass substrate 1 of all the four LCD panels A, B, C and D. A second problem is that the TFTs 3 of the pixel regions on the LCD panel C is damaged by the ESD (electrostatic discharge) during the rubbing process since the inner short ring 6 is removed from the upper edge and the left edge of the LCD panel C. More particularly, when a well known rubbing roller, not shown, initially touches the surface of the alignment layer of the LCD panel C at the upper left corner, the electrostatic charges are applied to the data lines or the gate lines, so that the TFTs 3 of the pixel regions are damaged. In contradistinction, the LCD panel A has the short ring 6 formed along the upper edge and the left edge, so that the electrostatic charges applied from the rubbing roller can be guided to the short ring 6, which is connected to the common electrode potential, whereby the TFTs of the pixel regions on the LCD panel A are protected from the ESD. The LCD panel B has the short ring 6 formed along the upper edge and the right edge, and the LCD panel D has the short ring 6 formed along the left edge and the bottom edge, so that the electrostatic charges applied from the rubbing roller can be guided to the short ring 6, whereby the TFTs of the pixel regions on the LCD panels B and D can be protected from the ESD.
As described before, the data lines, the gate lines and the pixel regions of each LCD panel are proximity and adjacent to the bonding region 19, so that the electrostatic charges, which are accumulated on the glass substrate 1 during the handling of each discrete LCD panel, and the rubbing process of the LCD panels, tend to discharge to the data lines or the gate lines, and in the worst case, the TFTs 3 of the pixel regions are damaged, resulting a defect called as a dot defect or a line defect. It is a third problem.
It is an object of the present invention to provide the LCD device with a structure which can prevent the light of a back light device from passing through the bonding region, and can prevent the TFTs of the pixel regions from being damaged by the accumulated electrostatic charges, during the handling of each discrete LCD panel, the rubbing process of the alignment layer on the lower glass substrate 1, the assembling process of the LCD panels, and the handling of the completed tiling panel.
A LCD device according to the present invention comprises:
a first LCD panel in which a pixel array substrate, on which a pixel array is formed, and an opposing substrate, on which a common electrode is formed, are sealed along a sealing region surrounding the pixel array; and
a second LCD panel in which a pixel array substrate, on which a pixel array is formed, and an opposing substrate, on which a common electrode is formed, are sealed along a sealing region surrounding the pixel array;
wherein one edge of the first LCD panel is positioned in proximity and adjacent to one edge of the second LCD panel; and
wherein a light shielding and electrically conductive adhesive bonds the one edge of the first LCD panel and the one edge of the second LCD panel.
The light shielding and electrically conductive adhesive is electrically connected to the common electrodes on the opposing substrates on the first and second LCD panels.
A short ring is formed along remaining edges of each of the pixel array substrates of the first and second LCD panels, respectively; and wherein the light shielding and electrically conductive adhesive is electrically connected to the short rings.
The sealing region along the one edge of each of the pixel array substrates of the first and second LCD panels is separated from the one edge to expose a surface region of each of the pixel array substrates, respectively;
a contact electrode is formed on each of the surface regions of the pixel array substrates of the first and second LCD panels, the contact electrode on the pixel array substrate of the first LCD panel is connected to the short ring on the pixel array substrate of the first LCD panel, and the contact electrode on the pixel array substrate of the second LCD panel is connected to the short ring on the pixel array substrate of the second LCD panel; and
the light shielding and electrically conductive adhesive is electrically and mechanically bonded to the contact electrode on the pixel array substrate of the first LCD panel and to the contact electrode on the pixel array substrate of the second LCD panel.
The short ring on the pixel array substrate is connected to the common electrode on the opposing substrate.
The first and second LCD panels are fixed to a transparent supporting substrate.
An upper surface of each of the first and second LCD panels is fixed to a first transparent supporting substrate, and a lower surface of each of the first and second LCD panels is fixed to a second transparent supporting substrate.
A short ring is formed along remaining edges of each of the pixel array substrates of the first and second LCD panels, respectively, a contact electrode connected to the short ring is formed on a surface, along the one edge, of the pixel array substrate of each of the first and second LCD panels, and an edge of the contact electrode is aligned to an edge of the sealing region along the one edge.
A LCD device according to the present invention comprises:
an upper left LCD panel in which a pixel array substrate, on which a pixel array is formed, and an opposing substrate, on which a common electrode is formed, are sealed along a sealing region surrounding the pixel array;
an upper right LCD panel in which a pixel array substrate, on which a pixel array is formed, and an opposing substrate, on which a common electrode is formed, are sealed along a sealing region surrounding the pixel array;
a lower right LCD panel in which a pixel array substrate, on which a pixel array is formed, and an opposing substrate, on which a common electrode is formed, are sealed along a sealing region surrounding the pixel array; and
a lower left LCD panel in which a pixel array substrate, on which a pixel array is formed, and an opposing substrate, on which a common electrode is formed, are sealed along a sealing region surrounding the pixel array;
wherein a right edge of the upper left LCD panel is positioned in proximity and adjacent to a left edge of the upper right LCD panel;
wherein a bottom edge of the upper right LCD panel is positioned in proximity and adjacent to a top edge of the lower right LCD panel;
wherein a left edge of the lower right LCD panel is positioned in proximity and adjacent to a right edge of the lower left LCD panel;
wherein a top edge of the lower left LCD panel is positioned in proximity and adjacent to a bottom edge of the upper left LCD panel; and
wherein a light shielding and electrically conductive adhesive bonds the right edge of the upper left LCD panel and the left edge of the upper right LCD panel, bonds the bottom edge of the upper right LCD panel and the top edge of the lower right LCD panel, bonds the left edge of the lower right LCD panel and the right edge of the lower left LCD panel, and bonds the top edge of the lower left LCD panel and the bottom edge of the upper left LCD panel.
The light shielding and electrically conductive adhesive is electrically connected to the common electrodes on each of the opposing substrates on the upper left LCD panel, the upper right LCD panel, the lower right LCD panel and the lower left LCD panel.
A short ring is formed along remaining edges of each of the pixel array substrates of the upper left LCD panel, the upper right LCD panel, the lower right LCD panel and the lower left LCD panel, respectively; and the light shielding and electrically conductive adhesive is electrically connected to the short rings.
The sealing region along the right edge and the bottom edge of the pixel array substrate of the upper left LCD panel is separated from right edge and the bottom edge to expose a surface region of the pixel array substrate, respectively, and a contact electrode is formed on the surface region along at least one of the right edge and the bottom edge;
the sealing region along the left edge and the bottom edge of the pixel array substrate of the upper right LCD panel is separated from left edge and the bottom edge to expose a surface region of the pixel array substrate, respectively, and a contact electrode is formed on the surface region along at least one of the left edge and the bottom edge;
the sealing region along the top edge and the left edge of the pixel array substrate of the lower right LCD panel is separated from top edge and the left edge to expose a surface region of the pixel array substrate, respectively, and a contact electrode is formed on the surface region along at least one of the top edge and the left edge;
the sealing region along the right edge and the top edge of the pixel array substrate of the lower left LCD panel is separated from right edge and the top edge to expose a surface region of the pixel array substrate, respectively, and a contact electrode is formed on the surface region along at least one of the right edge and the top edge;
the contact electrodes are connected to the short rings; and
the light shielding and electrically conductive adhesive is electrically and mechanically bonded to the contact electrodes.
The short ring on the pixel array substrate is connected to the common electrode on the opposing substrate.
The upper left LCD panel, the upper right LCD panel, the lower right LCD panel and the lower left LCD panel are fixed to a transparent supporting substrate.
An upper surface of each of the upper left LCD panel, the upper right LCD panel, the lower right LCD panel and the lower left LCD panel is fixed to a first transparent supporting substrate, and a lower surface of each of the upper left LCD panel, the upper right LCD panel, the lower right LCD panel and the lower left LCD panel is fixed to a second transparent supporting substrate.
A portion of the contact electrode is covered by the sealing region.
The contact electrode is separated from the edge of the pixel array substrate.
The contact electrode comprises a first portion formed on the surface region and a second portion formed between the sealing region and the pixel array, and the first portion and the second portion are connected.
The contact electrode comprises a first portion formed on the surface region and a second portion covered by the sealing region, and the first portion and the second portion are connected.
A short-ring is formed along a top edge and a left edge of the pixel array substrate of the upper left LCD panel, a contact electrode connected to the short ring is formed on a surface, along the right edge and the bottom edge, of the pixel array substrate, and an edge of the contact electrode is aligned to edges of the sealing region along the right edge and the bottom edge,
a short ring is formed along a top edge and a right edge of the pixel array substrate of the upper right LCD panel, a contact electrode connected to the short ring is formed on a surface, along the left edge and the bottom edge, of the pixel array substrate, and an edge of the contact electrode is aligned to edges of the sealing region along the left edge and the bottom edge,
a short ring is formed along a right edge and a bottom edge of the pixel array substrate of the lower right LCD panel, a contact electrode connected to the short ring is formed on a surface, along the top edge and the left edge, of the pixel array substrate, and an edge of the contact electrode is aligned to edges of the sealing region along the top edge and the left edge, and
a short ring is formed along a left edge and a bottom edge of the pixel array substrate of the lower left LCD panel, a contact electrode connected to the short ring is formed on a surface, along the right edge and the top edge, of the pixel array substrate, and an edge of the contact electrode is aligned to edges of the sealing region along the right edge and the top edge.
A contact electrodes is formed on an outside surface region, which exists outside of the sealing region, of the pixel array substrate of the upper left LCD panel, at each of an upper right corner region and the lower left corner region, respectively;
a contact electrodes is formed on an outside surface region, which exists outside of the sealing region, of the pixel array substrate of the upper right LCD panel, at each of a lower right corner region and an upper left corner region, respectively;
a contact electrodes is formed on an outside surface region, which exists outside of the sealing region, of the pixel array substrate of the lower right LCD panel, at each of an upper right corner region and the lower left corner region, respectively; and
a contact electrodes is formed on an outside surface region, which exists outside of the sealing region, of the pixel array substrate of the lower left LCD panel, at each of a lower right corner region and an upper left corner region, respectively.